1. Field of the Invention
The present invention relates to a path setting method and apparatus for setting multiple paths to provide a service for a subscriber. More particularly, the present invention relates to a path setting method and apparatus for securing a bandwidth for all paths required to provide a service for a subscriber.
2. Description of the Related Art
A system whereby multiple paths are set when a service is provided for a subscriber is well known. For example, a video-on-demand (VOD) service includes a well-known system whereby a control channel, a voice channel and an image channel, respectively, are set and a service is provided to a subscriber from a server via a switching system. However, there is a demand for increased efficiency for the setting of paths in this type of system.
FIG. 1 illustrates an example of a conventional switching system. As shown in FIG. 1, the switching system 30 includes a switching part 33, and circuit handling parts 32. A server 35 (service provision subscriber) regenerates and provides video images requested by subscribers 31 A, B, C. The circuit handling parts 32 include an optical-electrical exchange part to connect subscribers 31 or server 35 by an optical transmission path. When the switching system 30 shown in FIG. 1 is an asynchronous transfer mode (ATM) switching system, it includes smoothing and policing functions of the ATM cell.
The switching system 30 sets the control channel, the voice channel and the image channel between subscribers 31 and the server 35 for the service provided by the server 35. Thus, a VOD service, which sends the regenerated voices and images from the server 35, is provided by sending requests from subscribers 31 to server 35 via the control channel. In other words, the VOD service using the switching system 30 differs from a conventional video-on-demand service offered on cable television and elsewhere in that it makes multiple settings between subscribers 31 and server 35 for dedicated channels which have bandwidths which are the same or are different. For example, the control channel can have a 16 Kbps or a 64 Kbps bandwidth; the voice channel can have a 64 Kbps bandwidth; and, the image channel can be have a 3 Mbps or a 5 Mbps bandwidth.
FIG. 2 is an explanatory diagram of a prior art control sequence for setting the control channel, the voice channel and the image channel with the switching system shown in FIG. 1. As shown in FIG. 2, subscribers 31 A, B, C, D, the switching system 30 and the server 35 are indicated by vertical lines. For example, when subscriber A sends a SETUP (call setting request) message to set the control channel, the switching system secures the control channel bandwidth and sends the message to the server. Likewise, subscribers B, C and D send SETUP messages to set the control channels in the same manner. The server sends path completion response messages to subscribers A, B, C and D for the SETUP messages which set the control channels.
Next, subscribers A, B, C and D send SETUP messages to set the voice channels. The switching system secures a bandwidth for the voice channels. The server sends path completion response messages for the SETUP messages which set the voice channels to subscribers A, B, C and D.
Next, subscribers A, B, C and D send SETUP messages to set the image channels. The switching system secures the bandwidth for the image channels and sends SETUP messages to the server. The server sends path completion response messages for the SETUP messages which set the image channels to subscribers A, B, C and D.
Since the control channel, the voice channel and the image channel are set between subscribers A, B, C and D and the server by the above-described type of operations, a request is sent to the server via the control channel so that video reproduction images and the like can be provided from the server via the voice channel and the image channel.
In the prior art system wherein a service, such as the VOD service and other similar types of services, is provided by setting multiple paths for a subscriber, if the bandwidth for the control channel is 64 Kbps, the bandwidth for the voice channel is 64 Kbps, the bandwidth for the image channel is 3 Mbps and the available bandwidth between the switching system and the server is 30 Mbps, then the control channel, voice channel, image channel are set, in that order. Thus, for example, when 235 subscribers call in at the same time and the control channel and the voice channel have been set, the total bandwidth is (64 Kbps+64 Kbps)×235=30,080 Kbps=30.08 Mbps, and the bandwidth exceeds 30 Mbps of available bandwidth by only 80 Kbps.
Thus, when the required bandwidth adds up to more than the available bandwidth, there is no remaining bandwidth and an image channel setting cannot be made for the subscribers who have called in. In this case, in accordance with the prior art, a path disable message is sent to all the subscribers who have called in. As a result, even if the available bandwidth is 30 Mbps and nine (9) subscribers can receive the VOD service ((64 Kbps+64 Kbps+3 Mbps)×9=28,152 Kbps<30 Mbps), when the subscribers call in at once and set the control channels and the voice channels, the available bandwidth between the switching system and the server disappears. Therefore, the image channel can no longer be set and, as a result, none of the subscribers can be provided the VOD service. Furthermore, there are problems in that service deteriorates.